Vehicles powered either fully or partially by batteries must at some point recharge the batteries. Particularly in the case of battery electric vehicles, the lack of an alternative power source, like one that a plug-in hybrid electric vehicle would have, causes the batteries to deplete faster and have a more limited range. Plug-in electric hybrids are generally less taxing on the batteries and built-in regenerative systems may suffice to recharge the batteries enough to go longer without having to plug-in the vehicle to recharge it.
The standard American electrical socket provides 120 volts A/C. This electricity supply is often insufficient to recharge the batteries of an electric vehicle in a period of time to allow for convenient use of the electric vehicle. A full recharge may not even be completed overnight and partial recharges often take too much time to be practical. Providing a higher voltage electricity supply can greatly reduce the amount of time needed to recharge an electric vehicle. Such high voltage sources are available in homes and other locations.
It is desirable to provide a convenient way of connecting the high voltage electricity source to an electric vehicle to recharge the batteries thereby making recharging quicker and using an electric vehicle more practical. It is also desirable to provide a convenient way to plug the electric vehicle supply equipment to a 220/240V electrical supply source using plugs and receptacles designed to meet National Electrical Manufacturers Association (NEMA) standards. This will reduce the cost of the product, installation, service repair, relocation and greatly simplifying the local electrical permitting process. This will also make the electric vehicle more practical, acceptable and provide a lower cost of ownership for the vehicle consumer.
It is further desirable that when using electric vehicle supply equipment with a 220/240V electrical supply that certain aspects of the circuit include self-testing capability to ensure a safer performance. The self-testing capability may include testing the relay circuits that connect and disconnect the power source to the electrical vehicle.